1 Most feminine nouns (i.e. all those not listed in Group 2)
2 Weak masculine nouns, also called n-nouns (i.e. all those ending in -e plus those listed here)
3 A few neuter nouns (listed here)

These masculine nouns are weak although they do not end in -e
der Bär /der Graf /der Präsident
der Bauer /der Held /der Prinz
der Dozent /der Herr /der Soldat
der Elefant /der Kamerad /der Spatz
der Fink /der Mensch /der Student
der Fürst /der Nachbar /der Vorfahr

These are the few neuter nouns in this group
das Auge /das Hemd /das Interesse
das Bett/ das Herz /das Ohr
das Ende /das Insek